SRC/dla_syrpvgrw.f(3)

NAME
SRC/dla_syrpvgrw.f

SYNOPSIS

  Functions/Subroutines
double precision function dla_syrpvgrw (uplo, n, info, a, lda, af, ldaf, ipiv, work)
DLA_SYRPVGRW computes the reciprocal pivot growth factor norm(A)/norm(U) for a symmetric indefinite matrix.

Function/Subroutine Documentation

  double precision function dla_syrpvgrw (character*1 uplo, integer n, integer info, double precision, dimension( lda, * ) a, integer lda, double precision, dimension( ldaf, * ) af, integer ldaf, integer, dimension( * ) ipiv, double precision, dimension( * ) work)

DLA_SYRPVGRW computes the reciprocal pivot growth factor norm(A)/norm(U) for a symmetric indefinite matrix.

Purpose:

    !>
    !>
    !> DLA_SYRPVGRW computes the reciprocal pivot growth factor
    !> norm(A)/norm(U). The  norm is used. If this is
    !> much less than 1, the stability of the LU factorization of the
    !> (equilibrated) matrix A could be poor. This also means that the
    !> solution X, estimated condition numbers, and error bounds could be
    !> unreliable.
    !>

Parameters
    UPLO

    !>          UPLO is CHARACTER*1
    !>       = 'U':  Upper triangle of A is stored;
    !>       = 'L':  Lower triangle of A is stored.
    !>

    N

    !>          N is INTEGER
    !>     The number of linear equations, i.e., the order of the
    !>     matrix A.  N >= 0.
    !>

    INFO

    !>          INFO is INTEGER
    !>     The value of INFO returned from DSYTRF, .i.e., the pivot in
    !>     column INFO is exactly 0.
    !>

    A

    !>          A is DOUBLE PRECISION array, dimension (LDA,N)
    !>     On entry, the N-by-N matrix A.
    !>

    LDA

    !>          LDA is INTEGER
    !>     The leading dimension of the array A.  LDA >= max(1,N).
    !>

    AF

    !>          AF is DOUBLE PRECISION array, dimension (LDAF,N)
    !>     The block diagonal matrix D and the multipliers used to
    !>     obtain the factor U or L as computed by DSYTRF.
    !>

    LDAF

    !>          LDAF is INTEGER
    !>     The leading dimension of the array AF.  LDAF >= max(1,N).
    !>

    IPIV

    !>          IPIV is INTEGER array, dimension (N)
    !>     Details of the interchanges and the block structure of D
    !>     as determined by DSYTRF.
    !>

    WORK

    !>          WORK is DOUBLE PRECISION array, dimension (2*N)
    !>

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 120 of file dla_syrpvgrw.f.

Author

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